(EN) The invention inter alia relates to a data transmission system comprising atransmitting and/or receiving unit (120) on the track side and a transmittingand/or receiving unit (10) on the vehicle side. According to an embodimentof the invention, the transmitting and/or receiving unit on the vehicle sidecomprises at least one transmitting and/or receiving element (20-26) on thevehicle side which is mounted in the region of a track vehicle door (30), saidunit being covered by the same and separated from the rail track (110) whenthe track vehicle door is closed and remaining uncovered by the same whenthe track vehicle door is open.